Abstract: Anhydrous hydrogen fluoride of high purity can be recovered from metallic fluoride salts containing phosphate values by digesting the metallic salts in an aqueous solution in a humid atmosphere at a sufficiently high temperature to release a gas containing hydrogen fluoride and negligible amount of P.sub.2 O.sub.5. The released gas is rectified in a rectification operation which includes a rectification zone in which the rectification occurs in the presence of sulfuric acid.

Abstract: Calcium fluoride is produced from pond waters resulting from phosphoric acid processing by treating the pond waters with calcium carbonate and/or calcium oxide in two stages to precipitate out the major part of the fluorine values from the waters as calcium fluoride. After removal of the calcium fluoride the filtrate is treated with calcium oxide to remove a substantial portion of the remaining fluorine values as calcium fluoride. After removal of these calcium fluoride solids, the filtrate is treated with another charge of calcium oxide to produce dicalcium phosphate (dical) which is separated from the aqueous phase. The aqueous phase is treated with an additional charge of calcium oxide to remove a substantial portion of the solids from the aqueous phase leaving waters that can be discharged as waste or recycled as process water.